1. Field of the Invention
The present invention relates to a cleaning apparatus for cleaning a substrate such as a semiconductor wafer, a glass substrate, or a liquid crystal panel with a cleaning member.
2. Description of the Related Art
As semiconductor devices become more highly integrated in recent years, circuit interconnections become thinner and the distances between those interconnections also become smaller. While processing a semiconductor substrate, particles such as minute semiconductor particles, dust particles, or small crystalline pieces tend to be attached to the semiconductor substrate. If particles existing on the semiconductor substrate are greater in size than the distances between interconnections on the semiconductor substrate, then short-circuits will possibly be developed between the interconnections. To avoid such a drawback, any particles present on the semiconductor substrate are required to be sufficiently smaller than the distances between interconnections on the semiconductor substrate. This holds true for the processing of other substrates including a glass substrate for use as a photomask, a liquid crystal panel, etc. To meet such a requirement, there has been demand for a cleaning apparatus capable of removing smaller particles in the submicron level from semiconductor substrates and other substrates.
FIG. 4 of the accompanying drawings shows in perspective a conventional cleaning apparatus for cleaning a substrate such as a semiconductor wafer. As shown in FIG. 4, the conventional cleaning apparatus has a plurality of workpiece chucks 105 for clamping a planar workpiece 104 such as a processed semiconductor wafer. The workpiece chucks 105 are mounted at equal angular intervals on a chuck base 103 along an outer circumferential edge thereof. The conventional cleaning apparatus also has a swing arm 102 angularly movable in the directions indicated by the arrow B about a vertical axis at one of its opposite ends by a motor 101 whose output shaft is coupled to the swing arm 102. A cleaning member 106 is attached to the forward end of the swing arm 102. The motor 101 is supported on an upper end of a vertical rod of an air cylinder 107. Therefore, the swing arm 102 is vertically movable by the air cylinder 107. Vertical movement of the swing arm 102 is limited by a mechanical stopper 108 combined with the air cylinder 107.
In operation, the chuck base 103 is rotated about a vertical axis in the direction indicated by the arrow A, and the swing arm 102 is angularly moved in the directions indicated by the arrow B. The cleaning member 106 may comprise an ultrasonic nozzle, a cavitation jet nozzle, a pencil-shaped sponge member, or the like.
To be more specific, the ultrasonic nozzle ejects liquid having ultrasonic vibrational energy applied thereto, and the cavitation jet nozzle ejects high pressure liquid containing cavitation therein. If the cleaning member 106 comprises the ultrasonic nozzle or the cavitation jet nozzle, then the positional relationship between the workpiece 104 and the cleaning member 106 needs to be controlled accurately because the frequency of the ultrasonic waves and the focus of the nozzle are related to the above positional relationship for the ultrasonic nozzle or the appropriate rise and fall of cavitation are related to the above positional relationship for cavitation jet nozzle. The cleaning member 106 supported by the swing arm 102 is vertically lifted or lowered by the air cylinder 107, and can accurately be positioned at a lower stroke end thereof by the mechanical stopper 108 that is located near a lower stroke end of the air cylinder 107.
However, in the conventional apparatus, for varying the positional relationship between the workpiece 104 and the cleaning member 106, it has been necessary to interrupt the operation of the cleaning apparatus, and then manually adjust the position of the cleaning member 106 relatively to the workpiece 104. If the cleaning member 106 comprises a cavitation jet nozzle, it has suffered a problem of insufficient reproducibility in cleaning a plurality of workpieces because individual cavitation jet nozzles tend to have different characteristics and the cleaning process is greatly affected by the accuracy of the vertical position of the surface, to be cleaned, of the workpiece 104 clamped by the workpiece chucks 105.